fn main() {
    let c1 = || "c1";
    let c2 = || "c2";
    let v = [c1, c2];

    let mut i = "c3";
    let c3 = || i;

    // let v = [c1, c2, c3];

    let c4: || {
        i.to_owned() + "c4"
    };
    // let v = [c1,c2,c4];
}
